The electrolytic decomposition of ionizable chemical compounds, e.g., alkali metal halides is a well known commercial process. In the electrolysis of such compounds, gaseous products, e.g., chlorine, are produced as a major product. In most commercial installations a series of electrolysis cells are operated in banks and the gaseous product from each of the cells is collected and delivered into a common duct, or header, running over the top of each of the cells. Whenever one of the cells in a particular bank is shut down for maintenance or servicing, e.g., for replacement of the diaphragm or electrodes, the gaseous product line running into the header, needs to be detached from the common header. In such detaching operation a considerable amount of the gaseous product in the header will be released into the cell room unless the header is sealed off during the detachment.
Various methods have been used in the past to seal off the end of the gas product line communicating with the header. Conventionally this sealing has been provided by valving means which valving means is troublesome to maintain in liquid and/or gas tight condition and expensive to fabricate due to the highly corrosive nature of the wet chlorine gas. Further, the gaseous products emanating from the cells contain considerable amounts of water vapor which on entering into the header and cooling condense therein. This condensate is carried along with the gaseous products and, being somewhat corrosive in nature is difficult and expensive to handle.